netopeer2-server TCP socket not properly closed

[yoousra]

Hello,

I have encountered the following issue in my test:

The test is in IPV6.
netopeer2-server starts connecting to the client which is not listening yet:

14:56:58.373 netopeer2-server(PID:2165): [INF]: LN: Listening on xxx:830 for SSH connections.
14:56:58.374 netopeer2-server(PID:2165): [INF]: LN: Call Home client "my_client" endpoint "endpt" connecting...
14:56:58.374 netopeer2-server(PID:2165): [INF]: LN: Trying to connect via IPv6 to yyy:4334. 
14:56:58.874 netopeer2-server(PID:2165): [INF]: LN: Timed out after 500 ms (Operation now in progress).

netopeer2-cli starts listening at 14:56:58.957 (listen --timeout 90 --ssh --login x) but after 10s, the listen fails with error SSH connect timeout.

Then after the 60s timer expiry (ietf-netconf-server max-wait), netopeer2-server tries to reconnect:

14:57:58.876 netopeer2-server(PID:2165): [INF]: LN: Call Home client "my_client" timeout of 60 seconds expired, reconnecting.
14:57:58.876 netopeer2-server(PID:2165): [INF]: LN: Trying to connect the pending socket 32.
14:57:58.883 netopeer2-server(PID:2165): [ERR]: LN: SSH key exchange error (Socket error: No such file or directory).

Could it be that at the first connection try by the server, the TCP socket was created but not properly closed, so netopeer2-cli when listening accepted the connection from that socket, except there's no one on the other side, hence the failure after 10s?

[michalvasko]

What libnetconf2 version are you using? The key exchange error is quite strange, nonetheless.

[yoousra]

Using:

netopeer2-v2.7.0-12-g2809ede
sysrepo-v4.2.10-37-gd59ac7e7
libnetconf2-v4.1.2-34-g50defb3
libyang-v4.2.2-105-gb9d150a2a

Thanks a lot.

[yoousra]

There's no client listening when the server tries to reconnect after 60s, hence the ssh key exchange error maybe?

[michalvasko]

Does the server continue to work after the error, tries to establish a new Call Home connection? Whatever the cause of the key exchange error, it is generated by libssh, not much we can do with that.

[yoousra]

I don't know if the server continues to work after, I will try to check that.
But for me there is another problem before the ssh key exchange error.

The server tries to connect and times out here I guess:

libnetconf2/src/session_client.c

Line 1674 in 2add91c

VRB(NULL, "Timed out after %d ms (%s).", timeout_ms, strerror(errno));

, I don't know after that is the socket left pending or closed? And what should be the right behavior in IPV6?

And when netopeer2-cli starts listening after, it seems that it accepts a TCP connection on that socket and times out after 10s (ssh connect timeout), isn't there a problem there? netopeer2-cli should not accept such connection on the first place, no?

Apart from this, the other thing I would like to understand is, when the client is not there yet and the server tries to connect, why sometimes I get Timed out after 500 ms and others Connection error (Connection refused) ?

Thank you!

[Roytak]

Should be fixed in the latest devel branch.